Keyway strip for concrete pavement forms



y 1959 J. A. RAPPAS KEYWAY STRIP FOR CONCRETE PAVEMENT FORMS Sheet Filed May 31, 1968 1 5 wi z 2 fr Allan/dri 7 Fig-4 Fig.3

. May 6, 1969 J. A. RAPPAS 3,442,188

KEYWAY STRIP FOR CONCRETE PAVEMENT FORMS Filed May 31; 1968 Sheet 2 of 2 United States Patent U.S. CI. 9439 16 Claims ABSTRACT OF THE DISCLOSURE A keyway strip, preferably of extruded plastic material, is of generally trapezoidal form, with a front wa l1,-two side walls extending obliquely rearwardly from opposite edges of the front wall and diverging from each other, and a rear wall parallel to the front wall and connecting the diverging side walls to each other intermediate their length so that when the rear edges of the side walls are laid against a concrete form, the rear face of the rear wall will be spaced a substantial distance from the concrete form, to provide space for receiving the head of a bolt which holds a dowel pin in place while concrete is being poured around it, with no need for the bolt to extend through the concrete form itself. Strengthening webs are also provided between the front wall and the rear wall of the keyway strip, these webs serving, in combination with the front and rear walls, to provide a rectangular channel for receiving a dowel member extending from one section of keyway strip into the end of the next section thereof, to keep adjacent sections in alinement with each other. When the strip is to be used for slip form paving, thin clips attached to the concrete form hold the keyway strip tight against the form without the need for wiring or bolting the keyway strip to the form, and tie rods within the channel at the rear of the keyway strip connect one section of strip to the next adjacent section to anchor it against longitudinal movement when the concrete form is slipped or dragged longitudinally along the partially hardened concrete to a new location for pouring additional concrete.

Cross-reference to related application This application is a continuation-in-part of copending application Ser. No. 551,401, filed May 19, 1966 and now abandoned.

Background of the invention The use of keyway strips extending longitudinally along the edge forms of concrete pavements is well known in the art and is fully explained, for example, in the present applicants own United States Patent 3,166,815, granted J an. 26, 1965, to which reference is made for further explanation of the use of such strips, to "avoid repetition thereof in the present application. The construction disclosed in the present application may be regarded as an improvement upon the construction disclosed in applicants said patent.

An object of the present invention is the provision of a generally improved and more satisfactory keyway strip.

Another object is the provision of a keyway strip so designed and constructed that it may be used more easily and economically than prior strips, in the laying of concrete pavements having expanison joints.

Still another object is the provision of a keyway strip which may be used effectively without the need for boring dowel bolt holes in the steel forms which define the edge of the concrete pavement strip being laid.

A further object is the provision of a keyway strip so designed that it may be used equally well in either of two ditTerent ways, that is, with steel forms which do not have dowel bolt holes therein, and with steel forms which do have such dowel bolt holes.

A still further objects is the provision of a keyway strip fulfilling some or all of the objects above mentioned, so constructed as to give adequate support and accurate alinement to the dowels and dowel bolts mounted in'and supported from the keyway strip, even when there are no dowel bolts holes in the steel form and the dowel bolts do not extend through the steel form.

Another object is the provision of a keyway strip so formed that any concrete which seeps between the keyway strip and the form may be easily cleaned out of the strip before it is reused.

A further object is the provision of a keyway strip so designed that it may be used efficiently when paving is being done by what is called the slip form method.

A still further object is the provision of simple and inexpensive means for anchoring two adjacent sections of keyway strip to each other to prevent longitudinal separation of the sections from each other, which separation might otherwise occur especially in slip form paving and possibly also in other methods of paving, when undesired.

A still further object is the provision of improved means for holding the keyway strip against the face of the concrete form in a sufiiciently tight manner, while still permitting the concrete form to be moved longitudinally as is done in slip form paving, without causing corresponding longitudinal movement of the keyway strip already embedded in concrete which has been poured and partially hardened.

Brief description of the drawings In the accompanying drawings which are incorporated herein by reference and form a material part of the disclosure, and which relate to illustrative embodiments of the invention:

FIG. 1 is a somewhat schematic elevation of the inner face of a steel form, with a keyway strip of the present invention applied thereto;

FIG. 2 is a cross section through a keyway strip according to a preferred embodiment of the present invention, the section being taken near one end of the strip and showing a dowel member engaged in the strip for alining the strip with the next adjacent strip;

FIG. 3 is a cross section through the strip as applied to a concrete form, and with the concrete poured around the keyway strip and the dowel, illustrating one manner of use where the dowel bolt does not extend through the steel form;

FIG. 4 is a view similar to FIG. 3, illustrating an alternate manner of use, where the dowel bolt extends through the steel form;

FIG. 5 is a horizontal section through the strip, illustrating another manner of use;

FIG. 6 is a view similar to FIGS. 3 and 4 illustrating one form of mounting or holding means on the concrete form, for holding the keyway strip in place against the form when the method of slip form paving is to be used;

FIG. 7 is a fragmentary horizontal section taken approximately on the line 77 of FIG. 6, illustrating particularly one construction for anchoring one keyway strip to the next adjacent keyway strip to prevent longitudinal separation between the strips when slip form paving is being done;

FIG. 8 is a vertical section taken approximately 0n the line 8--8 of FIG. 9, also illustrating the anchoring means;

FIG. 9 is a view similar to FIG. 6 showing an alternate form of mounting or holding means for holding the keyway strip against the concrete form, for use particularly in slip form paving;

FIG. is a view similar to FIG. 7, illustrating an alternate form of anchoring means for preventing longitudinal separation of adjacent sections of keyway strip; and

FIG. 11 is a schematic elevation or face view of a concrete form with a keyway strip applied thereto, somewhat similar to FIG. 1 but illustrating particularly the appearance of the form and keyway strip when the mounting means of FIG. 6 is used.

Description of the preferred embodiments The present keyway strip is similar in a general way to the keyway strip forming the subject matter of applicants Patent 3,166,815, but has certain important differences. The strip disclosed in applicants patent in very satisfactory for use with steel forms which have bolt holes through which the dowel bolt extends, as shown for example in FIG. 5 of the patent. However, there are circumstances where it is not practical to provide bolt holes in the forms. The new strip of the present invention is intended especially for these situations where there is no bolt hole in the form, but the present strip may also be used entirely satisfactorily where bolt holes are provided in the form. In other words, the present strip is more versatile than the strip of applicants prior patent, since the present strip may be used either with or without bolt holes in the steel form, whereas the strip of the patent is intended for use where bolt holes are provided in the form.

Specifications for the construction of highway pavements (or other pavements, such as aircraft runways) frequently differ from locality to locality. For example, some states require that the keyway which interlocks one pavement strip with the next adjacent pavement strip at one side thereof, shall extend continuously along the length of the meeting line between the two strips, regardless of the presence or absence of a expansion joints extending crosswise or transversely of the pavement strips. When this is permitted, it is practical or feasible to use steel forms (such as the forms shown at 11, 13, in said prior patent) which have bolt holes in the forms at regular intervals, as for example intervals of about 40 inches apart. Since the keyway is to extend continuously without regard to transverse expansion joints, the location of the bolt holes with respect to the expansion joints is immaterial. With such constructions, the keyway strip disclosed in said prior patent is entirely satisfactory.

In other states or localities, however, specifications require that the keyway interlocking adjacent pavement strips with each other shall stop at a certain distance, usually about 9 inches, from each transverse expansion joint. In states or localities where such omission of the keyway is required, in the vicinity of the transverse expansion joint, the specifications also provide that there must be a transverse tie bolt or dowel, tying one pavement strip to the next adjacent pavement strip, in a location at a certain specified relatively close distance on each side of each expansion joint, and other dowels at other specified intervals. Merely as an example and not as a limitation on the invention, the expansion joints may be 61 feet 6 inches from each other (which is a typical distance between expansion joints) and it may be required that the first transverse dowel adjacent each expan sion joint be located 12 inches from the expansion joint, the next one 27 inches beyond the first one, with subsequent dowels at intervals of 60 inches until approaching the other end of the pavement strip near the next expansion joint, when again the last two dowels may be 27 inches from each other, and the last one 12 inches from the expansion joint. Using eleven spaces of 60 inches or 5 feet each, plus two spaces of 27 inches each, plus two spaces of 12 inches each, it is seen that this adds up to a total of 61 feet 6 inches, which is the assumed distance between successive expansion joints. If the first dowel is 12 inches from the expansion joint and if the keyway strip stops 9 inches from the expansion joint, the first dowel will be 3 inches from the end of the keyway strip.

When such spacings of dowels or transverse tie bolts are required (or any other irregular spacings) it is not practical or feasible to use steel forms with bolt holes formed therein for receiving and supporting the dowels or the supporting bolts of the dowels. Even if the steel forms were specially bored with bolt holes at the required distances with relation to the expansion joints, this would be impractical not only because of the time and expense of boring the holes, but more especially because the holes would seldom be in the right locations when the steel forms are striped from the sides of the hardened pavement and moved to another location for laying another length of the pavement. It will be readily appreciated that the steel forms which define the edges of the pavement when the concrete is being laid, are much too expensive to be used only once and then discarded. They must be capable of reuse many times. When one section of pavement has solidified enough to permit the stripping of the steel forms from the lateral edges, the forms are moved perhaps half a mile, or two miles, or ten miles or more, to be used again and again as further sections of the pavement strip are progressively laid. It is very seldom that holes previously made in the steel forms, would happen to come at just the right locations between the expansion joints, when the forms are used the second time or subsequently.

According to the present invention, bolt holes in the forms are not necessary, yet the new keyway strip of the present invention provides adequate support and alinement for the dowels and their supporting bolts.

Referring now to the drawings, a typical steel form for defining the edge of the concrete pavement is shown, having a bottom flange 11 which rests on the ground, a vertical flange 13 which defines the edge of the concrete and holds the wet concrete in place until it solidifies, and a top flange 15, these parts being substantially the same'as the parts having the same reference numerals in said Patent 3,166,815. The keyway strip of the present invention, indicated in general at 21, is of extruded plastic material having great strength, and the plastic material may be of any of the compositions disclosed in said prior patent.

The strip of the present invention is of generally trapezoidal shape, in this respect being similar in a general way to the strip of said prior patent. However, there are some important differences. As shown especially in FIG. 2, the present strip has a front wall 23 which is arranged vertically when the strip is in the normal position of use, an 1ncl1ned top wall 25 extending rearwardly and upwardly from the upper edge of the wall 23, a similar inclined wall 27 extending rearwardly and downwardly from the bottom edge of the front wall 23, and a web 29 wh ch is substantially parallel to the front wall 23 and which serves to tie the inclined upper wall 25 to the inclined lower wall 27 at points approximately midway of the lengths of those walls 25 and 27. In addition, strengthening webs 31 and 33 extend horizontally (when in normal position of use) to tie the front wall 23 to the rear wall 29 at points a little inwardly from the locations \2 v7here the walls 23 and 29 join the inclined walls 25 and The shape of the strip as shown in FIG. 2 differs from the shape disclosed in said prior patent, particularly in that the inclined top and bottom walls 25 and 27 are substantially longer than the corresponding walls in the prior patent, and they extend rearwardly a substantial distance beyond the rear face of the rear wall 29, to allow suflicient space for receiving a bolt head or nut, and sutficient space to apply a wrench easily to the bolt head or nut, as will be further explained below. Expressing it another Way, the rear wall 29 in the present construction is located at an intermediate point of the thickness (from front to back) of the entire strip, instead of being located at the rear extremity of the strip, or rear ends of the inclined walls.

Merely to give typical examples of satisfactory dimensions, without thereby intending a limitation on the invention, the total thickness of the strip of the present invention, from front to back (that is, from the plane of the front face of the front wall 23 to a plane lying against the rear edges of the two inclined walls 25 and 27) may be about one inch to one and one-eighth inches. The width of the front face of the front wall 23 may be about one and one-half to one and five-eighths inches. The width of the rear face of the strip, measured straight across from the upper rear corner of the inclined wall or flange 25 to the lower rear corner of the inclined wall or flange 27, may be about two and one-half to two and five-eighths inches. The rear face of the rear wall 29 may be five-eighths inch to eleven-sixteenth inch rearwardly from the front face of the front wall 23, so that the cavity or chamber at the rear of the strip has a depth (front to back) of about three-eighths or seven-sixteenths of an inch. The front wall '23 and rear wall 29 may each have a thickness of about three-sixteenths inch, while the inclined walls 25 and 27 and the strengthening webs 31 and 33 may each have a thickness of about one-eighth inch. The webs 31 and 33 are so placed that the rectangular space enclosed between the walls 23 and 29 and the webs 31 and 33 is approximately one-fourth inch thick (front to back) by one inch wide (top to bottom). The juncture of the rear face of the rear wall 29 with the inner faces of the inclined walls 25 and 27 is filleted or rounded as illustrated, on a radius of about one-fourth inch, for example. The strip is preferably formed by extrusion molding, the material being any suitable plastic material having toughness and rigidity. Polyvinyl chloride is preferred, although it is not the only possible plastic material which is suitable for present purposes, and the specific polyvinyl chloride compositions mentioned in said prior patent give good results. The plastic material (whether it be polyvinyl chloride or something else) may be strengthened if desired by use of a suitable filler, as for example glass fibers or other strengthening fibers of any known kind which will not deteriorate or disintegrate at the extrusion temperature.

It has become customary in the industry to furnish keyway strips in lengths of ten feet. This is a satisfactory length for the strip of the present invention. The length of ten feet works out economically when used in constructing pavements in which expansion joints are sixty-one feet six inches apart, since the first strip can be placed on the form with its first end nine inches from the location of the expansion joint, and if six strips each having a length of ten feet are mounted in endwise abutting relation to each other, the last strip will have its end at a distance of nine inches from the next expansion joint. Thus the strips require no cutting, and may be used over and over again. When expansion joints are at distances other than sixtyone feet six inches, some cutting of the keyway strips may be required, but this is easily done in a minimum of time, since the plastic strips cut easily and quickly, with either a hand saw or a power saw.

Preferably each strip has an alining dowel permanently mounted in one end, in the rectangular space between the webs 31 and 33, and projecting from that end, to fit into the corresponding rectangular space of the next adjacent keyway strip. Of course there is no such dowel used at the far end of the last strip just before the expansion joint. The dowel, as shown at 41 in FIGS. 1 and 2, may be of plastic material if desired (as disclosed in said prior patent) but preferably is of a suitable metal such as hard aluminum, having a rectangular cross section of a size to fit snugly within the rectangular space between the webs 31 and 33 of the plastic strip. It may have a length of about five inches, of which about two-one-half or three inches is inserted in the end of the plastic strip and permanently held therein as by a couple of rivets 43 passing through alined holes in the plastic strip and the metal dowel strip. This leaves about two or two and one-half inches of the dowel strip projecting from the end of the plastic keyway strip, to be inserted snugly into the rectangular opening in the end of the next adjacent plastic keyway strip when the strips are mounted in normal position of use, against the face of the steel form 13.

The preferred manner of use of the strip of the present invention is illustrated in FIG. 3. At the required intervals, having regard to locations of the expansion joints, the plastic strips are provided with transverse holes 51 extending through the front Wall 23 and back wall 29 of the plastic strip, these holes having a diameter for receiving reasonably snugly the bolts which are to support the dowels or tie rods which are to be imbedded in the concrete pavement, to tie one pavement strip or lane to the next adjacent pavement strip or lane. Such bolts usually have a diameter of about five-eighths of an inch, and consequently the holes bored through the walls 23 and 29 of the plastic keyway strip are of a diameter just enough larger than this, so that the bolts can be readily inserted through the holes without undue effort. The holes may be bored on the job if desired, which can be done easily because drilling holes in the plastic material is an easy operation. It is usually preferred, however, to have the holes pre-drilled before the keyway strips are brought to the job site.

Before the keyways strips are applied to the steel forms, the bolts 53 are inserted through the holes 51, each bolt being screwed into a sleeve 55 which is tightened up enough to draw the bolt head 57 snugly against the rear face of the rear wall 29 of the plastic strip. The sleeve 55 projects beyond the end of the bolt 53,. and the threaded dowel or tie rod 59 is screwed into the projecting portion of the sleeve 55, as seen in FIG. 3. The lbolt head 57 has a thickness (in a direction axially of the bolt) of about five-sixteenths of an inch, or in any event not more than three-eighths of an inch, so that there is room for this bolt head in the cavity behind the rear face of the rear wall 29, when the rear face of the plastic keyway strip is later applied to the vertical flat face of the steel form 13.

After the bolts 53 and dowels 59 have been applied to the plastic keyway strip, the keyway strip itself (with bolts and dowels attached) is then applied to the inner vertical face of the steel form 13 and is held tightly and snugly against the form 13 by tying wires 61 extending through small holes 63 provided at intervals along the length of the form member 13, at elevations just above the top edge and just below the bottom edge of the keyway strip, as shown in FIG. 3. The tie wires 61 are then tightened by twisting as indicated schematically at 65, to draw the keyway strip tightly against the face of the form.

It is found in practice that 16-gauge annealed steel wire is suitable for Wiring the keyway strip to the form, and if this size of wire is used, the holes 63 in the form may be /a inch or inch in diameter, which gives adequate clearance for getting the tie wire through the hole easily without undue effort. The tie wire holes can be spaced along the length of the form 13 at any suitable intervals, intervals of about 24 inches to 40 inches or more being found suitable. The tie wire holes 63 may be drilled on the job if desired, but preferably are pre-drilled before delivering the steel forms to the job site.

This construction is extremely efficient and economical, since it may be used over and over again, and the presence or absence of expansion joints does not interfere with the effective use of the keyway strips with pre-drilled holes for the bolts or the use of the steel forms 13 with predrilled holes 63 for the tie wires. The locations of the tie wire holes 63, in directions along the keyway strip, are

independent of the expansion joint locations and of the locations of the tie rods or transverse dowels 59.

In FIG. 1, the inner face of one of the steel forms 13 is indicated schematically, and two of the transverse filler members for making expansion joints are shown at 71. The plastic keyway strip, indicated in general at 21, stops short of the expansion joint locations 7-1, the ends of the keyway strip being, for example, nine inches from the expansion joint locations, as explained above. The first transverse dowel, counting inwardly from each expansion joint, is schematically indicated at 73 and is located, for example, at 12 inches from its adjacent expansion joint, which makes it 3 inches from the end of the keyway strip. The next transverse dowel 75 may be, for example, 27 inches from the dowel 73, or 39 inches from the expansion joint. Successive dowels 77 are at successive intervals of 60 inches from each other. As above explained when these dimensions were first mentioned, these dimensions are merely typical examples and are not intended as a limitation.

When the keyway strip has been set in place, with the transverse dowels in position, it is seen that the dowels are fully and adequately supported in proper alined relation by the plastic keyway strip. The bolts 53 are weld held by the keyway strip, since each bolt has a good bearing on the keyway strip, at two points spaced about inch apart (the distance from the front face of the front wall 23 to the rear face of the rear wall 29) thus preventing the bolt and its attached transverse dowel from wobbling or getting seriously out of alinement.

After the concrete has been poured against the inner face of the form 13 and around the keyway strip and the transverse dowels, as indicated schematically at 81, and after it has sufficiently set or hardened, the tie wires 61 are cut and the forms 13 are stripped away from the edge of the concrete, temporarily leaving the keyway strip in place. With the forms stripped away, access can now be had to the bolt heads 57, and these bolts are removed. The keyway strips themselves are then pulled out of the recesses which they caused in the concrete, the alinement dowels 41 extending from one keyway strip into the next keyway strip being of assistance in quickly removing successive strips from the concrete, as explained in said prior patent. If desired, the keyway strips may be slightly bowed in a longitudinal direction as explained in said patent, so the ends of the keyway strips will tend to spring out of the channels in the concrete.

When the keyway strips are removed, this will leave the sleeves 55 and the dowels 5 9 embedded in the solidified concrete. Then other dowels are screwed into the sleeves 55, to project outwardly from the edge of the already set concrete into the space where the next adja-cent lane of concrete pavement will be poured, and when the concrete of the next adjacent lane is poured, the dowels will thus tie one lane of the concrete pavement to the next lane, in the familiar manner well known in the concrete pavement industry.

Although it is possible to use the keyway strips of the present invention in the manner described above, mounting them on the steel forms by means of tie wires, yet it is possible also to use the keyway strips of the present invention with bolts going through the steel forms if desired, in a manner similar to that shown in said prior patent in connection with applicants previous form of keyway strip. This is illustrated in FIG. 4 of the present application. The steel form 13 is provided with bolt holes 85 at the desired intervals (which is possible and economically feasible especially in those situations where the pavement has no transverse expansion joints) and bolts 53 go through the forms 13 and through the holes 51 in the plastic keyway strip and into the sleeve 55, just as in the arrangement previously described. The bolts 53 in this arrangement must be, of course, somewhat longer than the bolts 53 in the arrangement previously described. When the bolts go through the forms 13, the

pull of the bolts on the sleeves serves to hold the plastic keyway strip snugly against the face of the form 13, and it is not necessary to use tie wires. Of course the bolts must be removed before the stripping of the forms 13 from the solidified concrete; and after the forms are stripped, the keyway strip is pulled out of the channel in the concrete, the rest of the operation being similar to that already described.

In some cases it is desired to use reinforcing bars as tie rods to tie one pavement strip to the next adjacent pavement strip or lane, rather than to use dowel bolts. The keyway strip of the present invention is sufficiently versatile so that it may be used with reinforcing bars if desired, whereas most if not all of the prior art keyway strips cannot be so used.

Referring now to FIG. 5, which is a fragmentary horizontal section taken about midway of the height of the keyway strip, a steel reinforcing bar is shown at 91. It may have a diameter of about /2 inch or inch, and is usually made of soft steel which can be readily bent by application of reasonable force. It extends through the hole 51, then has its end (of any desired length) bent over at a right angle as at 93, before the keyway strip is wired to the steel form .13. The bent end lies in the channel formed at the rear of the keyway strip between the walls 25, 27, and 29, and thus does not interfere with tight engagement of the rear edges of the walls 25 and 27 with the steel form 13.

After the concrete has been poured around the keyway strip and has solidified or set, the form 13 is stripped off (after cutting the tie wires 61) whereupon the bent ends 93 of the reinforcing rods 91 become exposed or accessible. The ends 93 are then grasped and swung to straighten these ends straight with the already embedded portions 91, causing them to stick out horizontally perpendicular to the edge of the concrete pavement. Then the keyway strip may be stripped from the concrete and pulled off of the projecting ends of the reinforcing rods. When the next strip or lane of the concrete pavement is to be laid, the reinforcing rods are already in position to be embedded in the concrete of the new lane, and need no further attention or positioning. It is not necessary to place new or additional dowels in position before the next pavement strip is laid, as is necessary when using dowels of the kind shown in FIGS. 3 and 4, where dowels must be screwed into the sleeves 55 after the keyway strip is removed and before the next pavement lane is laid.

Another advantage of the present keyway strip, in addition to its above mentioned versatility enabling it to be used in different ways, is that the large channel in the rear face of the keyway strip is entirely unobstructed and is formed by smooth surfaces free from any flanges or ribs or undercut portions, to which or in which solidified concrete may stick. At various places along the length of the keyway strip there is likely to be some seepage or leakage of concrete between the steel form 13 and the attached keyway strip. While this is undesirable and unintentional, some leakage is unavoidable. When it does occur, the concrete which seeps into the back of the keyway strip will harden or set, of course, and it is highly desirable that the keyway be so shaped that the solidified concrete can be easily and quickly removed, to condition the keyway strip ready for re-use. This is easily done with the present construction, as there are no flanges or overhangs in the back channel of the keyway strip, and nothing to prevent solidified concrete from being knocked loose by a simple blow. As distinguished from this, one prior construction has a rear channel into which rearwardly extending flanges project, and there are inwardly facing ribs at the rear edges of such flanges, thus making it extremely difficult to dislodge concrete which solidifies between these flanges and under the ribs. Moreover, in the prior construction just mentioned the rearwardly extending flanges would interfere with a nut or a bolt head, and also prevent the easy application of a wrench to the nut or the bolt head, so that the prior construction just mentioned is not at all suitable for use as a wired-on keyway strip in the manner of present FIG. 3, but must be used only when the bolt goes through the steel form, in the manner of present FIG. 4.

Typical dimensions for the key-way have been mentioned above, but it is emphasized again that these dimensions are only examples. Various highway departments in various states have slightly varying specifications as to size of the keyway, and may want it somewhat thicker or thinner in a horizontal direction (from the front face of the front wall 23 to the vertical plane of the rear edges of the legs or walls 25 and 27) or somewhat wider or narroiwer in a vertical direction (from the rear edge of the wall 25 to the rear edge of the wall 27).

As for length, the strips are conveniently manufactured in 10 foot lengths, as above stated, but can be of any reasonable length desired, and can be cut on the job when necessary. If there are 10 feet long, 6 of the strips are just right for the customary spacing of,61 feet 6 inches between expansion joints, leaving a 9 inch gap between the end of the keyway strip and the expansion joint filler. If the dowel bolt holes or tie rod holes are pre-bored before delivery to the job, and if they are spaced at the intervals above mentioned, the keyway.strips would be supplied in two kinds, two strips of the first kind being use-d at the ends of each pavement section (next to the expansion joint separators), reversed end for end of course, and four strips of the second kind being used between the end strips of the first kind. Each strip of the second kind would have two dowel bolt holes, feet apart and each 2 feet 6 inches from its adjacent end of the strip. Each strip of the first kind would have the same two holes plus a third hole 3 inches from one end, which may be called the expansion joint end.

If alinement dowels 41 (FIGS. 1 and 2) are to be riveted in place before delivery to the job, instead of being inserted at the job site, each keyway strip of the first kind or expansion joint kind would have such a dowel fastened in its end remote from the expansion joint, all but one of the keyway strips of the second kind would have an alinement dowel fastened in one end, and one of the keyway strips of the second kind would have no dowel fastened in either end, thus being able to receive dowels from the adjacent keyway strips at both ends.

The foregoing explanation shows how the keyway strip may be used in various ways, where the steel forms at the edge of the pavement are removed in a lateral direction after the pavement has sufiiciently solidified. In addition to these uses, the present keyway strip may also be used advantageously when paving by another method sometimes called slip form paving. In slip form paving, the steel forms at the edge of the pavement are not left in place until the pavement becomes hard and then removed laterally, but on the contrary, the steel forms at the edge of the pavement are dragged along in a longitudinal direction as the paving progresses, the forward movement being either intermittent or continuous, as desired by the paving contractor. The bottom of the steel forms slides along over the ground, like the runner of a sled. The forward end of the steel form is kept a little in advance of the point where the concrete is being poured, and the trailing end of the steel form is a little behind the point where the concrete is poured. The form gives lateral support to the freshly poured concrete sufficiently long so that the concrete sets partially and will hold its shape at the edge of the pavement, when the trailing edge of the form is moved forwardly and no longer furnishes lateral support for the concrete. The length of the steel form may be, for example, 60 or 100 feet, or any other convenient length desired by the paving contractor.

When doing slip form paving, the dowel holding bolts 53 must not extend through the form 13, as in FIG. 4, but must extend only through the keyway strip itself, as in FIG. 3. Also, tie wires such as shown at 61 in FIG. 3 cannot be used, as the tie Wires would interfere with the desired longitudinal movement of the form. Although the wires might be able to slide a limited distance along the stationary keyway strip when the form is moved longitudinally, the wires could not move past the next dowel bolt 53. Therefore, other means must be used to hold the keyway strip tight against the face of the steel form prior to and at the time of pouring the concrete, and such holding means must not interfere with the longitudinal movement of the form while the keyway strip remains stationary.

One form of such holding means is. shown in FIG. 6, where the inner face of the form 13 is provided with retaining clips 101 of thin metal, preferably somewhat springy or resilient, fastened to the inner face of the form by welding, or by screws 103 screwed into the clips from the outside of the form as shown. Each of these retaining clips has one leg lying flat against the face of the form 13, and another leg extending out at an oblique angle thereto, tight against the oblique or slanting side of the keyway strip, as readily seen in FIG. 6. It will be observed that one retaining clip holds the lower side of the keyway strip, and another retaining clip holds the upper side thereof.

These clips 101 are of metal which is quite thin, such as steel having a thickness of about or of an inch. With metal of this thickness, it is found that the clips do not prevent the longitudinal advancing movement of the steel forms to which the clips are attached. Since the concrete is only partly but not firmly set at the time the form is advanced longitudinally, the thin clips will simply compress the concrete slightly as they move longitudinally past any given point.

The dimensions of the clips 101, in a direction longitudinally of the keyway strip, and also the spacing of successive clips from each other, may be varied considerably. Merely as an example, each clip may be about two inches wide, in a direction longitudinally of the keyway strip, and successive clips may be spaced from each other at intervals of about two or three feet.

In the form shown in FIG. 6, the clips extend only part way along the length of the slanting leg or side wall of the keyway strip, toward the front wall thereof. Alternatively, as shown in FIG. 9, each clip 101 may extend somewhat farther, all the way from the steel form 13 to the front wall 23 of the keyway strip and may terminate in a bent end 105 engaging over the marginal edge of the front wall 23 of the keyway strip. Howeper, sufficient space is left between the ends of the top and bottom retaining clips so that the clips will not interfere with the bolts 53 or sleeves 55 (see FIG. 3) when the steel form 13 with the retaining clips attached thereto is dragged longitudinally along the keyway strip which remains longitudinally fixed in the concrete already laid.

Another feature of the invention which facilitates the use of the keyway strip in paving by the slip form method, is the provision of locking means or tying means to prevent longitudinal separation of adjacent keyway strips from each other. As mentioned above, the keyway strips are preferably in sections about ten feet long. The previously mentioned alinement dowels 41 (FIGS. 1 and 2) hold the adjacent keyway strips in proper alinement with each other, Incidentially, these alinement dowels 41 must not be confused with the transverse dowels 59 (or 91) which serve to tie adjacent lanes of pavement to each other in a lateral direction. Now it may happen that, during slip form paving, the lateral form or edge form 13 is moved longitudinally forwardly at a time when the concrete has been poured around one or more of the transverse dowels 59 which are bolted (by the bolts 53) to one section of keyway strip, but no concrete has yet been poured around any of the dowels 59 bolted to the next adjacent section of keyway strip. Under these conditions, the first strip will stay in proper position notwithstanding the longitudinal movement of the form 13, because of its dowels 59 being embedded in concrete. But the next strip, having no dowels embedded as yet in concrete, will tend to move forward with the form 13, because of friction of the keyway strip against the form 13 and against the retaining clips 101. To prevent such longitudinal movement of the keyway strip section, the invention provides locking means or tying means. In the first form of such means, there is a tying bar 113 which extends longitudinally in the space between the inclined side flanges of the keyway strip, at the junction between two strips, and has bent ends 115 extending at right angles to the length of the bar 113. One end 115 extends snugly through a hole in the wall 29 of one keyway strip, and the other end 115 extends snugly through a similar hole in the wall 29 of the next adjacent keyway strip, to tie the strips to each other to prevent longitudinal separation thereof.

Instead of having the bent ends 115 of the rod 113 extend through holes 116 in the wall 29, it is sometimes preferred to have metal eyes secured to the rear face of the wall 29, with the eye horizontal and the axis of the hole in the eye vertical. These eyes would be in substan tially the same locations as the holes 116. The bent ends 115 of the rod would then extend vertically downwardly into the respective eyes, with the rod resting on the eyes. This has the advantage that gravity tends to hold the rod in the eyes, as seen in FIGS. 8 and 9 where an eye is shown at 117.

The bar or rod 113 is preferably of steel rod stock having a diameter of about 7 inch or A inch, and a length of about 10 inches. With a bar of this length, the holes in the walls 29 for receiving the ends 115 of the locking bar would be about 5 inches from the end of each keyway strip. This will give adequate clearance from the alinement dowels 41 without interfering in any way with these dowels, assuming that each alinement dowel 41 is about 6 inches in length, extending about 3 inches into the end of each keyway strip.

With a locking bar such as this in place, each keyway strip is locked longitudinally to the next adjacent strip so that it cannot move longitudinally with the form 13 when the form is slid longitudinally to its next position.

An alternative form of locking means, for accomplishing the same purpose, is illustrated in FIG. 11. Here, instead of using a separate bar 113, the alinement dowel 41 itself is used to tie one keyway strip to the next adjacent strip. It will be recalled from the previous description that one end of the dowel 41 is fixed in its keyway strip by suitable fastening means such as rivets 43. According to this embodiment of the invention, the projecting portion of the alinement dowel 41, intended to project into the next adjacent strip, is provided with a hole or bore 121, and the wall 29 of the next adjacent keyway strip is provided with a hole 123 alined with the hole 121 when the two keyway strips are assembled tight against each other as shown in FIG. 10. Then a retaining pin 125 is inserted through these alined holes 121 and 123, thus preventing longitudinal withdrawal of the dowel 41 from the keyway strip, and thereby locking the two keyway strips to each other, since the other end of the same dowel is already fastened to its keyway strip by the rivets 43.

For ease of withdrawal of the pin 125 when the form 13 has moved onward beyond this junction and when the keyway strips are to be stripped out of the solidified concrete, it is preferable to form the pin 125 of the shape shown in FIG. 10, with an enlarged head 127 in position to lie against the steel form 13 when the other end of the pin 125 extends through the thickness of the dowel 41 and into contact with the rear face of the front wall 23 of the keyway strip. The enlarged head 127 is sufficiently thin so that it does not fill the space between the wall 29 and the form 13, but allows a considerable open space between the wall 29 and the enlarged head 127. Thus it is easy to insert a claw bar or other prying member between the head 127 and the keyway strip wall 29, to pry the pin out if it is too tight to drop out easily.

In slip forming paving, the transverse expansion joint forming members 71 (FIG. 1) may be used, just as in ordinary paving, except that they must not be fastened to the forms 13, since the forms 13 must be free to move longitudinally while the transverse expansion joint members 71 and the keyway strips remain stationary. However, in slip form paving it is more customary not to use any such transverse members 71, and if they are not used, the keyway strip will extend continuously without interruption along the form 13, the entire strip being made up of separate sections each about 10 feet long, as above explained. Of course as the steel forms 13 move forwardly, additional sections or lengths of keyway strip are added to the inner vertical face of the form 13, and these added sections of keyway strip remain stationary (tied or locked to the preceding sections, as above explained) when the form 13 moves forwardly again, so that lengths of keyway strip are constantly being added.

It is to be understood that the disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.

What is claimed is:

1. A keyway strip for use in molding a keyway groove in the edge of a pavement or the like, said keyway strip comprising a body of relatively hard and relatively rigid material formed to provide, in cross section,

(a) a front wall,

(b) a rear wall substantially parallel to said front wall,

(0) two oblique walls diverging from each other in a direction from front to back and extending from opposite lateral edges of said front wall to respective opposite lateral edges of said rear wall and joined thereto and continuing rearwardly a substantial distance beyond said rear wall, to define a rearwardly open channel behind said rear wall,

(d) two strengthening webs connected to and extending between the front and rear walls in directions substantially parallel to each other and perpendicular to said front and rear walls at locations spaced inwardly from the junctions between said rear wall and said two oblique walls, to form a rectangular space between said front and rear walls and between said two webs,

(e) said channel behind said rear wall being unobstructed and free of flanges and webs and other parts likely to interlock with concrete in said channel, so that any solidified concrete in said channel may be easily removed therefrom.

2. A keyway strip as defined in claim 1, wherein (f) said channel also is sufiiciently thick in a direction perpendicular to said rear wall to accommodate within the channel the thickness of the head of a dowel bolt extending perpendicularly through openings in said front and rear walls and sufficiently wide to enable a wrench to be readily applied to such a bolt' head.

3. A construction as defined in claim 1, in which said walls and webs are integrally molded from plastic material.

4. A construction as defined in claim 1, in which said walls and webs are integrally formed from plastic material by extrusion molding.

5. A keyway strip as defined in claim 1, further including an alining dowel comprising a rigid bar of rectangular cross section having one end portion inserted in said rectangular space and permanently fastened therein, and a second end portion projecting beyond the ends of the walls of said strip and adapted to be inserted in the rectangular space of another keyway strip.

6. The combination with a keyway strip as defined in claim 1 of an upright form member for defining an edge of a concrete pavement strip to be laid, said keyway strip being mounted on said form member with the rear edges of the two oblique walls of the keyway strip engaged tightly with said form member, a series of pairs of holes extending through said form member at intervals spaced along the length of said keyway strip, one hole of each pair being just above said keyway strip and the other hole of each pair being just below said keyway strip, and a series of tie Wires, one extending through the holes of each pair and around the front wall of said keyway strip to hold said keyway strip tight against said form member.

7. The construction as defined in claim 6, further including a series of holes through said front wall and rear wall of said keyway strip at spaced intervals along the length of said strip, and a series of transverse dowel members supported from said holes, each dowel member or its support extending through alined holes in said front and rear walls and having a portion lying between said rear wall and said form member and so shaped that it will not pass forwardly through the hole in said rear wall.

8. The construction as defined in claim 7, wherein each of said transverse dowel members is a reinforcing bar having a portion extending out through alined holes in said front and rear walls and projecting into the area of the concrete pavement strip to be laid, and having another portion bent laterally with respect to the first mentioned portion and extending in a direction longitudinally of said keyway strip and lying in said channel of the keyway strip, in the space between the form member and the rear wall of the keyway strip.

9. The construction as defined in claim 7, wherein each of said transverse dowel members is supported by a threaded bolt having a bolt head located in said channel of the keyway strip, in the space between the form member and the rear wall of the keyway strip, and having a shank extending forwardly out through alined holes in said front and rear walls and a threaded portion outwardly beyond said front wall, and a threaded sleeve having its rear end threaded onto said threaded portion of said bolt and its forward end engaged with said dowel member in supporting relation thereto.

10. The combination with the construction defined in claim 6, of an expansion joint member extending in a direction substantially perpendicular to said form member and having one end abutting against that face of said form member on which said keyway strip is mounted, said keyway strip being so placed on said form member that there is a substantial gap between said expansion joint member and the near end of said keyway strip, and alined holes through said front wall and rear wall of said keyway strip in a first location close to said near end of said keyway strip and also in a second location spaced along said keyway strip at a greater distance from the first hole location than the distance from said expansion joint member to said first hole location, said alined holes in said front and rear walls serving as means for mounting transverse dowels on said keyway strip.

11. A construction as defined in claim 1, further including tying means for tying one keyway strip to the next adjacent keyway strip, to prevent longitudinal separation of the strips from each other.

12. A construction as defined in claim 11, wherein said tying means comprises a tension resisting member lying in the space between a keyway strip and a concrete form to which it is applied, said tension resisting member bridging the joint between two adjacent and longitudinally alined keyway strips with one end engaged with one of such keyway strips and the other end engaged with the other of such strips.

13. The combination with a keyway strip as defined in claim 1, of a concrete form member having a vertical wall, and a series of metal clips fastened to and projecting from said vertical wall for retaining said keyway strip tight against said wall while permitting longitudinal sliding movement between said strip and said wall.

14. A construction as defined in claim 13, wherein certain of said clips are affixed to said wall below said keyway strip and extend obliquely upwardly in eugagement with the lower oblique side wall of said keyway strip, and others of said clips are afiixed to said wall below said keyway strip and extend obliquely downwardly in engagement with the upper oblique side wall of said keyway strip.

15. A construction as defined in claim 14, further including means connecting the end portions of two adjacent strips to each other to prevent longitudinal separation of the strips from each other, so that if said form wall is moved longitudinally while a first strip mounted thereon is prevented from moving longitudinally by concrete poured against said first strip, a second strip connected thereto by said connecting means will also be prevented from moving longitudinally.

16. The combination with a keyway strip as defined in claim 1, of a concrete form member having a vertical wall, and retaining members fastened to and projecting from said vertical wall for retaining said keyway strip tight against said wall while permitting longitudinal sliding movement between said strip and said wall.

No references cited.

JACOB L. NACKENOFF, Primary Examiner.

US. 01. X.R. 94-4, 46; 249-9 

